Increasingly, natural waterways in the world have been utilized for hydroelectric power and tapped as fresh water sources for residential, industrial, and agricultural use. The use of this water for these purposes has severely interfered with the natural ecology of these waters and has threatened the survival of migratory fish such as salmon and trout.
Some of these problems that have been created include the fact that the upward and downward migration of fish are blocked by structures such as dams and hydroelectric installations. Various apparatus and structures have been improvised to provide a pathway around these installations for migrating fish. However, the pressure upon the fish as they are discharged downstream in the previous systems gives them embolisms and leaves them highly susceptible to predators. Also, the upward migrating fish are confused due to their natural instinct to follow the main water flow which draws them to the white water discharge of the hydroelectric generators, etc., rather than to the installations designed to allow the fish to circumvent these obstacles. Accordingly, the preferred embodiment acts to reduce the distractions caused by water discharge techniques presently used by providing a low pressure discharge system and a fish ladder which uses a dominant water flow and hence is more attractive to the fish.
Also, when water is diverted from a waterway, e.g., to an irrigation canal or to a pumping station, it is desirable to screen or prevent fish from entering these unnatural paths. Therefore, the screening system of the preferred embodiment allows for a significant portion of water to be diverted from the waterway without altering the natural flow pattern of the waterway. The fish are not removed from the waterway and thus are not destroyed by the pumping equipment, nor are they pumped into irrigation canals where they will die.